Cryosurgery is the application of extreme cold to destroy abnormal or diseased tissue and can be used to treat a number of skin diseases and disorders. Cryosurgery is generally employed in the medical field for the removal of skin lesions from the body of a mammal, including the human body. When extreme cold is applied to abnormal cells, ice crystals can form inside the cells, which can rupture their cell membranes, thus destroying the cells. The extreme cold can also freeze blood vessels supplying blood to the abnormal cells.
Traditionally, liquid nitrogen has been used as the coolant solution in cryosurgery. However, other coolant solutions have been used and are known by those of skill in the art. Historically, the coolant solution was applied to the abnormal tissue with a cotton or foam swab.
More recently, however, methods were developed to spray the coolant solution onto the abnormal tissue. In these methods, the coolant solution is typically stored in a pressurized container, and, upon demand, an uncontrolled amount of coolant solution is dispensed from the container into a supply tube. In some methods, the coolant solution can exit the supply tube and be dispersed into a cone, cup, or speculum placed around the abnormal tissue to pool the solution. In other methods, the supply tube can have a porous tip applicator, for example a cotton or plastic foam applicator, located at the distal end of the tube. The coolant solution can accumulate in the applicator, and the applicator can be applied to the surface of the abnormal tissue.
When coolant solution is applied to a treatment area, the coolant solution must remain in contact with the treatment area for a period of time until what is called an ice ball, by those of ordinary skill in the art, is formed. The ice ball must be maintained for approximately 30 seconds and should be big enough to cover the treatment area, which includes the abnormal tissue as well as an area 1-2 mm around the abnormal tissue in all directions.
After the ice ball is formed, it is maintained for a sufficient period of time. During this time, the coolant solution vaporizes and evaporates. Part of the evaporation process is called bubbling by those of ordinary skill in the art, and it is desirable for a practitioner to be able to view bubbles during the bubbling process. As the bubbles begin to dissipate, a thawing process can begin. If a practitioner wishes to maintain the ice ball for a longer period of time, more coolant solution should be applied to the treatment area when the bubbles begin to dissipate.
Typically an ice ball will need to thaw for approximately one minute. Most destruction of the abnormal cells in the treatment area occurs during the thawing phase. The freeze and thaw cycle described above can be repeated as necessary depending on the size of the treatment area.
Devices used in connection with the above-described methods known by those of skill in the art incorporate several disadvantages. First, the coolant solution is often wasted.
When an uncontrolled amount of coolant solution is dispensed from the container, a large portion of the coolant solution is wasted due to the uncontrolled dispensing from the container and what is called blowback by those of skill in the art. When this happens, an excessive amount of coolant solution is released into the surrounding atmosphere rather than directed onto the abnormal tissue.
When a cone is used by a practitioner in connection with applying coolant solution to a treatment area, both hands are often required for application. As such, often a second person is required to assist when treating difficult to reach areas.
When a porous tip applicator is used to apply the coolant solution to abnormal tissue, an excessive amount of coolant solution is often delivered through the supply tube to saturate the applicator. When this happens, coolant solution is dispensed directly into the atmosphere and thus, coolant solution is wasted. Furthermore, not all of the coolant solution absorbed in or on the applicator reaches the abnormal tissue. A portion of the coolant solution remains in or on the applicator when applied to the treatment area. Additionally, the shapes of these applicators do not allow the coolant solution to be distributed evenly or onto a precisely demarcated area.
Another disadvantage of devices used in connection with the above-described methods is that the coolant solution is dispersed in an uncontrolled manner. Thus, coolant solution is often sprayed or splashed outside of the intended treatment area onto the patient's body or a practitioner's hands or arm.
There is thus a continuing, ongoing need for a cryosurgical device for cryosurgically treating skin lesions that provides for effective treatment of the abnormal tissue, that does not waste the coolant solution used in connection with the device, and that evenly distributes a controlled amount of coolant solution to a well defined area.